1. Field of the Invention
The present invention relates to a digital phase shifter for shifting in phase an input wave having a predetermined waveform such as a sinusoidal continuous wave, for example.
2. Prior Art
As a means of providing a continuous wave having a predetermined phase shift, digital phase shifters have conventionally been used. For example, in a vector scope which displays relative amplitudes and phases of a plurality of chrominance components in a composite video signal, a digital phase shifter has been used to shift in phase a subcarrier received as an input by a predetermined amount. One such digital phase shifter is disclosed in Japanese Patent Appln. Public-Disclosure No. 62-207012 (A Digital Phase Shifter), which has a structure utilizing the frequency heterodyne effect.
Also, Japanese Patent Appln. Public-Disclosure No. 4-229703 (A method of Generating Phase Correlated Waveforms) discloses a method of generating waveforms by a direct digital synthesizer (DDS) having a waveform look-up table.
Since the above-mentioned digital phase shifter of Public-Disclosure No. 62-207012 utilizes the frequency heterodyne effect, its circuit configuration is complicated.